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Diffusers with Extended Frequency Range

Schroeder diffusers are unable to diffuse sound when all their wells radiate in phase, a phenomenon known as flat plate effect. This phenomenon appears at multiple frequencies of pf0, where p is the integer that generates the well depths and f0 the design frequency. A solution is to send the flat plate frequencies above the bandwidth of interest. For QRDs and PRDs to achieve this goal, impractically long sequences are needed. This paper presents Power Residue diffusers, of small length in comparison to their prime generator, as solutions to the problem. Their characteristics are investigated and their performance when applied to Schroeder diffusers is explored while modulation is used to cope with periodicity. The results confirm the expectations.